Non-bituminous sound deadening material

ABSTRACT

A sheet or pad of sound deadening material comprising: (a) a polymeric component free of bitumen or asphalt such as natural or synthetic rubber, PVC, chlorinated polyethylene or ethylene vinyl acetate copolymer; (b) a filler such as calcium carbonate, barytes, talc, mica, magnesium carbonate or silica; (c) a compatibilising agent such as ricinoleic acid; and a tackifier such as pine rosin. Formulations may include a flame retardant, a polar additive, a polymer anti-oxidant, a heat stabilizer for PVC and a lubricant. Methods for forming such sheets or pads and for applying such sheets or pads to a metal panel are also provided.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention is concerned with improvements in or relating to sounddeadening materials and generally relates to sound deadening material ofthe heat fusible type in sheet or pad form or for cold applicationemploying adhesives for bonding.

Sound deadening materials of the heat fusible type are well known andused in large quantities in automobiles, dishwashing machines and otherapplications where it is desired to reduce the noise arising fromresonant vibrations of the sheet metal panels.

Heat fusible sound deadening material in sheet or pad form, is mostoften adhered to metal panels by simply laying a pad of sound deadeningmaterial on a metal panel and heating the two together. This mayconveniently be applied as the panels travel along a conveyor belttowards an oven. The self adhesive properties of a sound deadeningmaterial at elevated temperatures may be utilised to create a bond ofone with the other.

Alternatively, an adhesive may be applied to either or both surfaces toenable a bond to be made at room temperature. In either case the bondneeds to have high tenacity in order to meet the conditions ofapplication in the factory and subsequent to that, e.g. up to 180° C. inthe oven and later possible extreme cold in usage with the need toobviate the possibility of the sound deadening material breaking awaywith time and vibration. A requirement of such a sound deadeningmaterial is that it have excellent adhesion properties.

When a sound deadening material is applied to a surface which would beadversely affected by heating e.g. when laminated to timber for noisereduction in buildings, the method of laminating one to the other may bewith adhesives applied in the usual manner. Likewise there aresituations where it is simply more convenient to use adhesive bonding.

2. Discussion of the Prior Art

Well known heat fusible sound deadening materials are those based onbitumen and hence necessarily black in colour. Bituminous materials ofthis type are disclosed in Australian Patent Specification Nos. 34339,405091, 498,074, 560006 and 606877. There are practical disadvantages inusing such bitumen based materials which include their appearance andinferior sound deadening properties.

U.S. Pat. No. 3,424,270 and its division U.S. Pat. No. 3,652,360 areconcerned with sound blocking structural elements for airborne sound.The Specifications disclose the use of a number of polymers includingPVC and acrylonitrile rubbers. The combination of PVC and acrylonitrilerubbers is well known in the art and has been used since 1942. Indeed,L. A. Utrachi, Polymer Blends and Alloys, Hanser Publishers, 1989, pp 4,"The PVC/NBR blend was the first commercial thermoplastic blend in themodern sense of the word. " U.S. Pat. No. 3,424,270 and its divisionU.S. Pat. No. 3,652,360 also disclose the use of natural rubber andbarium sulphate composition in the cured and uncured form, as part of asound deadening laminate. However, the efficiency of the materialsprovided by such proposals is, to some extent, limited by the amount offiller which can be incorporated into the formulation withoutcompromising the adhesion and flexibility of the material in sheet orpad form.

U.S. Pat. No. 4,420,341, "Stabilized Surface Modified Fillers" proposesthe treatment of various fillers including calcium carbonate withvarious saturated and unsaturated fatty acids generally in combinationwith each other. The Specification requires that the fatty acid isalways used in combination with an antioxidant to prevent thedegradation of the "surfied filler" both during and after addition ofthe fatty acid to the filler. In addition the technique disclosed inU.S. Pat. No. 4,420,341 teaches that it is advantageous to promote theacid filler reaction in the shortest time possible so that exposure toair and heat are minimised. The specification teaches that with veryfine fillers it can be advantageous to also purge the filler before andduring surfation with an inert gas such as nitrogen to prevent or reduceexposure to air before use. Such procedures are not suited to theeconomical production of sound deadening materials in high volumes.

A number of prior art patents disclose the use of esters of ricinoleicacid as coupling agents applied to fillers including calcium carbonate.U.S. Pat. No. 4,704,238 uses a number of aliphatic alcohol/fatty acidesters including esters of ricinoleic acid. UK Patent Application GB 2031 910 A, discloses the use of fatty acid esters of mono and polyhydricalcohols as coupling agents particularly for calcium carbonate andpolymeric materials. Included among the fatty acids for the manufactureof such esters is ricinoleic acid. However, none of these priorspecifications show the use of such techniques to produce superior sounddeadening materials.

French Patent 1,489,806 discloses a process for improving reinforcingfillers for elastomers in which very fine fillers show improveddispersion following treatment with dispersing agents. Variousdispersing agents are proposed. The specification teaches that theproperties of reinforcing fillers are more favourable when theirfineness is greater. However, the specification is specifically directedto silica and silicate fillers and does not address the suitability ofsuch treated fillers for use in sound deadening materials. Moreover thetreatment procedures exemplified are not suited to the economicalproduction of sound deadening materials in high volumes.

SUMMARY OF THE INVENTION

It is an object of this invention to provide in one embodiment animproved sound deadening material in sheet form which exhibits superiorsound deadening properties and which contains no bitumen or asphalt.

The present invention accordingly provides, in one embodiment, a sounddeadening material in sheet or pad form comprising:

a polymeric component substantially free of bitumen or asphalt;

a filler;

a compatibilising agent; and

a tackifier.

A sound deadening material according to the present invention may alsoinclude a flame retardant, a polar additive, a polymer anti-oxidant, aheat stabiliser for PVC, a lubricant and optionally other additives.

The present invention also provides, in another embodiment a method forforming a sound deadening material in sheet or pad form comprising thesteps of:

compatibilising a filler by treatment with a compatibilising agent toform a pre-blend;

mixing the pre-blend with other ingredients including a polymericcomponent substantially free of bitumen or asphalt and a tackifier toform a mix; and

forming a sheet or pad from said mix.

The present invention also provides, in yet another embodiment, a methodfor applying a sound deadening material to a metal panel comprising thesteps of;

forming a sheet or pad of sound deadening material by compatibilising afiller by treatment with a compatibilising agent to form a pre-blend,mixing the pre-blend with other ingredients including a polymericcomponent substantially free of bitumen or asphalt and a tackifier toform a mix, and forming said sheet or pad from said mix;

laying said sheet or pad on a metal panel; and

heating said metal panel and said sheet or pad whereby to bond saidsheet or pad to said metal panel.

The polymeric component of a sound deadening material according to thepresent invention may be an elastomer. The elastomer may comprise arubber component and both natural and synthetic rubbers have been foundsuitable for use as the rubber component in accordance with theinvention.

Acrylonitrile butadiene rubber (also referred to herein as nitrilerubber), butyl rubber either straight, chlorinated or brominated,ethylene propylene rubber, polychloroprene, polysulphide rubber orstyrene butadiene rubber are preferred synthetic rubbers for use inaccordance with the invention. Acrylonitrile butadiene rubber (NBR)containing 25 to 50% acrylonitrile and having a Mooney viscosity of 20to 80 is particularly preferred. NBR may be employed at 0 to 17% and inthe preferred formulations is used at 4 to 10%.

We have found that polyvinyl chloride (PVC) when used as a polymericcomponent in accordance with the invention, enhances the sound deadeningefficiency of a heat fusible sound deadening material in the highertemperature region, imparts flame retardant properties to theformulation and may increase slump. The preferred PVC contains 14% vinylacetate as the co-monomer and has a K-Value of 45. Such a PVC resinshows good long term heat stability when suitably stabilized, preferablywith lead stabilizers. PVC may be used in formulations where there isthe requirement of good sound deadening efficiency and slump and wherethere is no objection to its use.

Any low K-value PVC may be employed as a polymeric component inaccordance with the present invention. The PVC is preferablyco-polymerised with vinyl acetate to give a degree of internalplasticisation, increased capacity for high filler loading and greaterheat stability. Chlorinated polyethylene can also be employed. Theparticularly preferred grade of PVC is Lacovyl SA 6001 from AtochemFrance. This has a K-value of 45 and a vinyl acetate content of 14%.When PVC is used in the formulations of the invention it is preferablypresent in an amount of not more than 18% by weight of the totalformulation. In the most preferred formulations PVC, when present, isused at a level of 3 to 12% by weight of the formulation.

Any of the known heat stabilizers for PVC may be used in accordance withthe present invention. The most efficient stabiliser and the preferredtype is based on basic lead sulphate in a non-dusting form. This ispreferably employed at a percentage of 0.5 to 1.5%, when PVC is presentin the formulation.

Other polymers including chlorinated polyethylene or high vinyl acetatecontent (i.e.28% or greater VA content) ethylene vinyl acetate, may alsobe used as a polymeric component in accordance with the presentinvention. In general it has not been found that the sound deadeningefficiency with such polymers is as great as that with formulationscontaining PVC. However, such formulations are generally still superiorto the sound deadening efficiency of the bituminous materials previouslyused.

Any powder form filler may be employed in accordance with the invention.The preferred filler is calcium carbonate (calcite, whiting, limestone,chalk) in powdered form, which may be from any source, cost being themain determinant. Other powder form fillers may be employed includingbarytes, talc, mica, magnesium carbonate, silica or mixtures thereof.However, it has been found that the best balance of properties andlowest. cost is obtained with calcium carbonate. The filler level ispreferably between 60 and 90% by weight of the total formulation. In theparticularly preferred formulations calcium carbonate is used in anamount of from 79 to 89% by weight of the total formulation.

Each ingredient plays an important role in the properties of aparticular heat fusible sound deadening material formulation madeaccording to the present invention. For example, the use on the fillerof a compatibilising agent applied from 0.1 to 5% by weight of the totalformulation, enables the use of higher volume fractions of filler whilestill retaining suitable processing characteristics and also enablesimproved hot slump, impact strength and cold bend resistance, comparedwith formulations without such a compatibilising agent. Higher levels offiller are also important for cost, a big consideration for such aproduct. However, it is not necessary according to the present inventionto use antioxidants or inert atmospheres with the fillers in the mannerproposed by the prior art referred to above in order to achieve markedlysuperior properties in sound deadening materials free of bitumen andasphalt.

Riconoleic acid is the preferred compatibilising agent according to theinvention. Ricinoleic acid of low acid value namely 130-145, has beenfound to be particularly preferred for use as a compatibilising agentaccording to the present invention.

Ricinoleic acid can be made with different levels of acid value with acommon form having an acid value in the range of 170-186. For purposesof clarity we here give the designation to that common form with thehigher acid value `HAV`, whilst the lower acid value form we heredesignate `LAV`. The LAV form we have found to be more efficacious andis the particularly preferred type for use in accordance with thepresent invention.

The particularly preferred ricinoleic acid LAV referred to herein hasthe following typical analysis:

    ______________________________________                                        Appearance    Pale amber liquid, cloudy when cold,                                          which deposits a small amount of                                              related fatty acid on aging.                                    Colour (Gardner)                                                                            7 max.                                                          Acid value    130-145                                                         Water content %                                                                             1.5 max                                                         Hydroxyl value                                                                              145-160                                                         Iodine value  80-90                                                           Saponification value                                                                        180-195                                                         ______________________________________                                    

By way of contrast the following is a typical analysis for Ricinoleicacid HAV:

    ______________________________________                                        Appearance     Amber liquid with some `foots` cold                            Acid value     170-186                                                        Water content %                                                                              3 max                                                          Iodine value   80-90                                                          Saponification value                                                                         180-195                                                        ______________________________________                                    

The ricinoleic acid is applied to the filler(s) in a suitable mixer, toform a pre-blend. The mixer is preferably of a type which elevates thetemperature of the blend to between 40° and 110° C. in order to shortenthe reaction time of the two ingredients. The pre-blend is made withonly the filler(s) and the riconoleic acid being present. The pre-blendis later blended with the remaining ingredients of the formulation.

In one alternative method also suitable for use in accordance with thepresent invention, the filler and ricinoleic acid may be blendedtogether at ambient temperatures with a reaction period being allowedbefore use sufficient for the reaction between these two ingredients tohave occurred. The reaction period required should be determined bytesting.

The reaction is believed to be that of the acid portion of the moleculeof the ricinoleic acid with the filler and acts to facilitate thecompatibilising or coupling of the filler with the elastomeric and anypolymeric ingredients. Unless such a reaction is allowed to occur withthe filler, the acidic nature of riconoleic acid potentially could reactwith the polymeric ingredients to the possible detriment of thoseingredients. Furthermore the reaction product of riconoleic acid and,for example, calcium carbonate, facilitates "wetting" of that calciumcarbonate by the polymeric ingredients.

It has been found that if the riconoleic acid is simply added to thetotal mix (and not pre-blended with the filler), the resultant productis difficult to process, dry in appearance, brittle, has poor hot slumpand lower bond strength for a given formulation.

Other compatibilising agents may be employed such as the Titanates andsilanes. We have found the greatest efficiency and lowest cost to datewith riconoleic acid LAV. When employed in the formulations made underthis invention, it is preferably used at the rate of 0.5 to 2.5% of thetotal formulation.

A tackifier of the pine rosin type, hydrocarbon resin type or coumeroneindene type may also be used in accordance with the present invention.Such tackifiers appear to act on the rubber component in a similarmanner to that of an extender or processing oil to aid flexibility aswell as to tackify. Furthermore, the preferred pine rosin materialslower the melt viscosity of the formulation and add substantially to thesound deadening efficiency.

The tackifier may also act to increase the hot slump of a heat fusiblesound deadening material. When a tackifier is used in increasing amountsin some formulations, an increasing degree of slump may be observed.

Beyond a certain percentage of tackifier relevant to the formulationconcerned, the heat fusible sound deadening material may become tootacky and floppy to employ readily, yet the material still retains goodsound deadening properties.

Tackifiers may be used to increase the bond to metal or to thelaminating ply at the elevated temperatures employed for adhering heatfusible sound deadening materials. Preferably they are not tacky at roomtemperature. They also have the effect of extending the rubber componentdue to their good compatibility with rubber, thus increasing the rubberlike properties. The tackifier preferred for use in accordance with thepresent invention is a pine rosin type also variously known as tall oilrosins, pine oleoresins and their esters.

Within the range of pine rosins and their esters some show an increasein slump for a given formulation whilst others exhibit little of thiseffect. There are also some which cause the heat fusible sound deadeningmaterial to become weak in extension and very floppy for a givenformulation. Furthermore there are those which enhance the cold bendresistance and impact strength more than others. The two grades whichhave been found to impart the best balance between slump, bond strength,impact strength, extensibility and sound deadening efficiency, arePinechem 240 and Pinerez 1200 NC, from Eka Nobel. The tackifiers arepreferably used at a percentage of 2 to 9%, most preferably 5 to 8%.

Hydrocarbon resins, frequently made as a by-product in the petrochemicalindustry, are similarly beneficial as tackifiers according to thepresent invention, but do not exhibit the same increase in sounddeadening efficiency.

Whilst liquid plasticisers may be employed to increase plasticity, thereis a concern that they could leach out or volatalise with time to causee.g. window-fogging in cars.

Polar additives such as carboxylic acids, added to the sound deadeningmaterial composition at the compounding stage (as opposed to thecompatibilising agent which is pre-blended with the filler) have beenfound to assist in sound deadening efficiency, particularly in enhancinglower temperature sound deadening performance. Oxalic acid is apreferred carboxylic acid and has the effect of increasing the peaksound deadening efficiency and in some formulations, shifting that peakto a lower temperature. Thus such substances may be employed as a meansto control the temperature level where peak efficiency occurs e.g. fordifferent climatic zones or different application areas. Similar effectsin shifting the curve and sound deadening enhancement may also beobtained from other substances such as phthalic, malonic or maleic acidor their anhydrides. Where the acidity of such substances is of concernin a formulation, this can be overcome through the use of a suitablequantity of lime in the formulation.

Atactic polypropylene, a by-product from the manufacture of isotacticpolypropylene may be employed as part of the formulation of a sounddeadening material according to the present invention. When employed,atactic polypropylene enhances hot slump, lowers melt viscosity andassists in the production of smoother sheet. It also tends to lower thetemperature at which peak sound deadening efficiency occurs.

Lubricants may be used to improve the hot slump and to generally improvethe processing of a sound deadening material. Waxes, stearic acid (usedas part of the main mix as opposed to the compatibilising agent which ispre-mixed with the filler) and calcium stearate as well as other wellknown fatty acid ester lubricants may be employed, but are notessential.

Flame retardant properties may be imparted by the use of antimonycompounds or halogenated chemicals or with the use of aluminatri-hydrate. The latter is preferred for reasons of cost and toxicity.When desired, up to 30% of the filler may be replaced with aluminatri-hydrate. If there is no PVC present in the formulation to otherwiseconfer a degree of flame retardancy to the formulation, aluminatri-hydrate is preferably used when flame retardancy is required.

An anti-oxidant effective for the rubber component of the formulationmay also be used in accordance with the present invention. The hinderedphenols may be used for such purposes and act to lessen the hardeningcaused by oxidation during processing and by aging, which couldotherwise lead to embrittlement of the sound deadening material. It isnot essential but long term properties are improved by its presence. Apreferred anti-oxidant is2,4-bis(n-octylthio)-6-(4-hydroxy-3,5-di-tert-butylanilino)-1,3,5,-triazine, also known as Irganox 565 from Ciba Geigy. If used it isemployed at the rate of 0.01 to 0.5% of the overall formulation.

In one particularly preferred form the invention comprises a sounddeadening material composition including PVC (optionally containingvinyl acetate as a co-monomer) (in a proportion of 0 to 15% by weight),acrylonitrile butadiene rubber (in a proportion of 0 to 15% by weight),a compatibilising agent (optionally riconoleic acid LAV) (in aproportion of 0.1 to 5% by weight), a filler (optionally calciumcarbonate) (in a proportion of 40 to 90% by weight), alumina tri-hydrate(in a proportion of 0 to 30% by weight), tackifier (optionally pinerosin) (in a proportion of 4 to 10% by weight), Oxalic acid a proportionof 0 to 0.5% by weight), anti-oxidant (optionally Irganox 565) (in aproportion of 0 to 1.0% by weight), a heat stabiliser for PVC, ifpresent, (in a proportion of 0.3 to 1.5% by weight) and a lubricant ifrequired (in a proportion of 0 to 4% by weight).

Sound deadening materials according to formulations provided by thepresent invention may be prepared by pre-blending the filler andcompatibilising agent in a mixer such as a ribbon blender andsubsequently mixing the pre-blend so formed with the other ingredientsin an intensive mixer such as a mixer where the ingredients are mixed,melted and homogenised. This may be followed by extrusion andcalandering to convert the melt into sheet form. Other methods offorming sheets of sound deadening material according to the presentinvention include direct extrusion or calandering of sheet.

The use of relatively thin steel panels in automobiles, leads to anunacceptable level of sound transmission without the use of a sounddeadening material. In the automotive industry, weight is a veryimportant factor effecting fuel consumption amongst other things. Hencea heat fusible sound deadening material which has greater efficiency isclearly beneficial. This is especially true for a heat fusible sounddeadening material having superior sound deadening efficiency over thetemperature range at which the sound deadening material is to be used.

Heat fusible sound deadening material of the bituminous type made toAustralian Patent Specification No. 606877 (in the name of SoundDeadeners Australia Pty. Ltd., --now known as Tri-Tex Australia Pty.Ltd.) has a sound decay rate measured by the Geiger Thick Plate Method,under Australian Standard K154.10, of at least 27 dB per second at 21°C., for 2.5 mm thickness of sound deadening material. One Australianautomobile manufacturer has a requirement of a minimum decay rate of 15decibels per second at 21° C. and a minimum of 6 decibels per second atall temperatures from -1° to +38° C. for heat fusible sound deadeningmaterial of 2.0 mm thickness.

Heat fusible sound deadening materials have been made in accordance withthe present invention which have a minimum decay rate in excess of 27 dBper second at 21° C. for 2.0 mm thickness of sound deadening materialwhen measured under the same test.

In the case of formulations designed for warm climates or usage, thesound deadening level exhibited by materials made in accordance with thepresent invention has also exceeded 27 dB/sec for the whole range from21° to over 35° C., a temperature range which would appear moreapplicable to warm climates such as Australia. By way of contrast, heatfusible sound deadening material made in accordance with AustralianPatent Specification No. 606877, in the range 21° to 35° C. has beenfound to measure approximately 27 to 10 dB/sec. decay rate respectively.In the case of formulations designed for cool climates or usage, thesound deadening level of materials made according to the present.invention have shown values, which are also in excess of 27 dB/sec.,between 10° and 25° C.

Heat fusible sound deadening material can more realistically be assessedon the basis of sound decay rate in decibels for a certain mass of sounddeadening material applied to the same Geiger Thick Plate using the sameMethod of test. Mass is an important consideration in automobiles andmany other applications and this method takes into account theefficiency of the heat fusible sound deadening material with respect tomass.

One automobile manufacturer requires the mass of sound deadeningmaterial to be calculated back to an application weight of 2.4 kg/sq.m.,which corresponds to 600 g. being applied to the Geiger Plate of 500×500mm. Under this method the above specified 15 dB decay rate for nominal 2mm thickness heat fusible sound deadening material translates toapproximately 10 dB/sec. at 21° C. This method is employed in the laterresults simply to give consistency to those figures.

Australian industry has employed bitumen based heat fusible sounddeadening material having a Sound decay rate of approx.20 dB/sec. at 21°C., falling to approximately 6 to 8 dB/sec. at 43° C. when calculatedback to 2.4 kg/sq.m.

Some formulations produced according to the present invention have arating of approximately twice those values at 21° C. Furthermore, hotclimate formulated heat fusible sound. deadening material made accordingto this invention have produced higher sound deadening efficiencyresults for the range of 30° to 40° C., than the above mentionedbituminous material at 21° C. Additionally, because the materialsproduced in accordance with this invention do not contain bitumen, anycolour may be produced with suitable pigmentation, thus e.g. enablingcolour coding.

Other application areas for such sheet made in accordance with thisinvention are for reducing the level of noise in air-conditioningducting and to reduce the noise produced by the "drumming" of rain onmetal roof decking or noise generation and transmission of metal sidingon buildings and machine housings.

The previously known bituminous materials referred to above showreasonable sound deadening efficiency at low temperatures e.g. 10° C.but generally show a considerable reduction in sound deadeningefficiency from their commonly quoted value at 21° C. to their value atsay 40° C. Formulations of heat fusible sound deadening materialdesigned for warmer climates and made according to the present inventionhave shown a sound deadening efficiency at 40° C., at least equal totheir value at 21° C.

Dishwashing machines frequently operate at temperatures of 65° C. andhigher. The previously known bituminous sound deadening material hasonly very low sound deadening efficiency at such temperatures. Inaccordance with the present invention material can be "tailor made" tobetter suit the temperature range that requires the maximum level ofsound deadening efficiency. The peak performance of sound decay versustemperature can be varied. through changes in formulation.

In the manufacture of dishwashing machines more efficient sounddeadening is constantly sought because of space limitations and the factthat often the machine is in the home. The considerably greaterefficiency of some formulations provided by the present invention athigher temperatures compared with the prior art bituminous materials,can lead to the use of lower thickness of heat fusible sound deadeningmaterial and consequent cost saving.

Greater efficiency in heat fusible sound deadening material has beenobtained according to the present invention through the use of differentingredients or in a different combination to those previously employedin the manufacture of such sound deadening materials. An essential partof the formulation relates to the use of agents which assist in givingbonding, coupling and wetting (i.e. compatibilising) between thenon-binder ingredients (e.g. fillers and pigments) and the binderingredients (e.g. rubber, tackifiers, polymers, etc.) The use ofcompatibilising agents particularly enables the employment of highervolume fractions of fillers (approximately 46 to 80% by volume or 70 to90% by weight for materials according to the present invention) whilestill retaining good processing characteristics and toughness.

The use of higher volume fractions of filler leads to better sounddeadening efficiency for a given system. Additionally the use ofingredients which are polar such as PVC, pine rosin and oxalic acid hasbeen found to lead to greater sound deadening efficiency. This increasein efficiency is believed to be due to the ability of such ingredientsto aid in the conversion of the mechanical energy of sound to that ofheat. Without the use of compatibilising agents, formulations providedby the present invention with their high volume fraction of fillerswould be stiff, brittle and difficult to manufacture by known methods,would show poor hot flow and tend to have inferior bonding to steel whensuitably heated.

One known requirement for a heat fusible sound deadening material foruse in the auto industry is known as the "heat flow test", which isreferred to herein as the "hot slump" test.

Under the hot slump test a flat strip of heat fusible sound deadeningmaterial is placed on a steel sheet, bridging over a half circle grooveof 25 mm radius and the whole is heated for 30 minutes at 160 deg. C.After cooling, not less than 95% of the contact face of that heatfusible sound deadening material must be firmly adhered to the steelincluding the radius.

This method tests both the adhesion to the steel and the ability of theheat fusible sound deadening material to "slump" to conform to theradius, without rupture, under its own weight. When required, heatfusible sound deadening material made in accordance with the presentinvention passes this test.

Different automotive manufacturers have different variations of thistest, however each demand a high degree of adhesion and the ability toslump to conform to shape. The balance between the various ingredientsis important to be able to pass this test.

Australian Patent Specification No. 34339 discloses the use of anadhesive ply in order for the bond of the bituminous heat fusible sounddeadening material to the steel to better withstand shock at lowtemperatures. It is a well known procedure in the plastics and rubberindustries to laminate different materials together in order to obtainan enhancement of properties. Refrigerator lining sheets have been madein a laminated form for many years, to obtain the toughness of thepolystyrene butadiene substrate with the gloss and better resistance tofoodstuffs of biaxially oriented G. P. polystyrene.

In a similar manner, when extremely high bond strength and/or resistanceto cold shock is required, an adhesive laminate (of a different natureto that in Australian Patent Specification No. 34339), may also beemployed in accordance with the present invention. This laminate or plymay be applied to the heat fusible sound deadening material at the timeof manufacture and on the side of the sheet that is subsequently to bebonded to another substrate, frequently sheet metal.

The lamination of such an adhesive layer to the sound deadening materialmay conveniently be applied in film form or by the known extrusionmethods or by other known coating methods. Suitable polymers forlaminating are of the ethylene acrylic acid copolymer type. We havefound that an adhesive film laminate thickness as low as 5 micron issufficient with such materials.

By applying such a laminate the strength of the bond between metal andsound deadening material may be increased to the point where repeatedblows at -14° C. will not dislodge the heat fusible sound deadeningmaterial from the steel substrate. Such a laminate is not sticky at roomtemperature and also serves as a useful means of obviating blocking ofsheets of heat fusible sound deadening material, when stacked togetherunder high loading at 45° C.

We have found that it may be convenient to employ a film which is itselfa co-extruded laminate, to laminate onto the heat fusible sounddeadening material of this invention. Such a co-extruded film mayconsist of a thin layer of ethylene butyl acrylate copolymer on eitherside of polyethylene, the latter acting as the cheaper "carrier" filmfor the more expensive adhesive film layers. Apart from theaforementioned advantages, it has been found that such a film laminatecan increase the sound deadening efficiency of a heat fusible sounddeadening material, particularly at lower temperatures.

A further requirement for a heat fusible sound deadening material forthe auto industry is to have sufficient impact strength and resistanceto cold bending such that on a cold day breakage will not occur at thetime of application, due to handling at temperatures as low as 5° C. Anautomotive requirement is for a strip 50 mm×150 mm of sound deadeningmaterial to be conditioned at -10° C. for four hours and then slowlybent 180° around a similarly conditioned 50 mm diameter mandrel withoutbreaking or cracking. When required sound deadening material made inaccordance with this specification passes this test.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

It is convenient to further describe the invention in relation to thefollowing examples showing various embodiments of the present inventionin the form of typical and preferred formulations showing a typicalrange of ingredients which may be used in accordance with the presentinvention. In each case one particularly preferred form of theformulation is also given.

Test runs were conducted in the laboratory for each of the preferredformulations given by placing 1500 g. of filler into a jacketed Bekenlaboratory sigma arm mixer together with the indicated quantity ofcompatibilising agent. Heating was applied and mixing continued forapproximately one hour by which time the mix temperature rose toapproximately 80° C. At this time all other ingredients were added tothe pre-blend, the top weight (dead weight ram) was applied and mixingproceeded to where the compound was fluxed. This compound was thensheeted out a laboratory two-roll mill.

To test the relevance of the laboratory trials to actual productionselected formulations, e.g. Example 6 (ii) were additionally prepared byplacing 100 kg. of filler in a ribbon blender which is capable of beingheated. The heater and the mixer motor were turned on and the requiredquantity of compatibilising agent added slowly to the rotating mix.Mixing and heating proceeded for one hour by which time the mixingtemperature was approximately 90° C. The pre-blend so formed was dumpedinto open containers for later use in manufacture of sheet or pad,sometimes immediately and other times days, weeks or even months later.No significant differences in results were noted whichever mixing methodwas adopted and whether the pre-blend was used immediately or only afterstanding for up to several months before further processing.

EXAMPLE 1

    ______________________________________                                        Weight Percentage                                                             Ingredient        Range   Preferred                                           ______________________________________                                        Calcium carbonate 40-90   79.4                                                Riconoleic acid LAV                                                                             0.1-5   1.2                                                 PVC copolymer      0-15   6.4                                                 Basic lead sulphate                                                                             0.3-1.5 0.8                                                 Nitrile rubber     0-15   4.2                                                 Oxalic acid         0-0.5  0.16                                               Pine rosin         4-10   7.9                                                 ______________________________________                                    

This preferred formulation was found to exhibit 80% hot slump, goodtoughness and excellent sound deadening efficiency.

EXAMPLE 2

    ______________________________________                                        Weight Percentage                                                             Ingredient        Range   Preferred                                           ______________________________________                                        Calcium carbonate 40-90   79.1                                                Riconoleic acid LAV                                                                             0.1-5   1.2                                                 PVC copolymer      0-15   6.3                                                 Basic lead sulphate                                                                             0.3-1.5 0.6                                                 Nitrile rubber     0-15   4.2                                                 Oxalic acid         0-0.5  0.16                                               Pine rosin         4-10   8.4                                                 Irganox 565       0-1      0.03                                               ______________________________________                                    

This preferred formulation showed 100% hot slump, good toughness andsimilar sound deadening efficiency to that of Example 1.

EXAMPLE 3

    ______________________________________                                        Weight Percentage                                                             Ingredient         Range   Preferred                                          ______________________________________                                        Calcium carbonate  40-90   81.4                                               Riconoleic acid LAV                                                                              0.1-5   1.2                                                PVC copolymer       0-15   6.5                                                Basic lead sulphate                                                                              0.3-1.5 1.5                                                Nitrile rubber      0-15   4.3                                                Coumerone indene resin                                                                             0-0.5 4.9                                                Irganox 565          0-0.5  0.03                                              ______________________________________                                    

This preferred formulation showed 50% hot slump, good toughness and hasgood sound deadening in the region between 30° and 55° C. making itsuitable for dishwasher application.

EXAMPLE 4 (i)

    ______________________________________                                        Weight Percentage                                                             Ingredient        Range   Preferred                                           ______________________________________                                        Calcium carbonate 40-90   79.8                                                Riconoleic acid LAV                                                                             0.1-5   1.5                                                 PVC copolymer      0-15   6.4                                                 PVC heat stabiliser                                                                             0.3-1.5 1.1                                                 Nitrile rubber     0-15   4.3                                                 Oxalic Acid         0-0.5 0.0                                                 Pine rosin         4-10   6.9                                                 Irganox 565       0-1      0.03                                               ______________________________________                                    

This preferred formulation 4 (i) was found to have 100% hot slump,reasonable toughness and good sound deadening efficiency for the range25° to 40° C. This formulation is therefore well suited to autoapplication for a warm climate such as Australia.

EXAMPLE 4 (ii)

    ______________________________________                                        Weight Percentage                                                             Ingredient        Preferred                                                   ______________________________________                                        Calcium carbonate 79.8                                                        Riconoleic acid LAV                                                                             1.6                                                         PVC copolymer     6.4                                                         PVC heat stabiliser                                                                             1.1                                                         Nitrile rubber    4.3                                                         Oxalic Acid       0.0                                                         Pine rosin        6.9                                                         Irganox 565        0.03                                                       ______________________________________                                    

By slightly increasing the percentage of Riconoleic acid LAV, thetemperature range for high sound deadening efficiency of Example 4(i),has been shifted downward to 18° C. to 30° C. This formulation is thuswell suited to auto applications that range from warm to temperateclimates.

EXAMPLE 4 (iii)

    ______________________________________                                        Weight Percentage                                                             Ingredient        Preferred                                                   ______________________________________                                        Calcium carbonate 79.4                                                        Riconoleic acid LAV                                                                             1.6                                                         PVC copolymer     6.4                                                         PVC heat stabiliser                                                                             1.1                                                         Nitrile rubber    4.2                                                         Oxalic acid       0.5                                                         Pine rosin        6.9                                                         Irganox 565        0.03                                                       ______________________________________                                    

By using the same percentage of Riconoleic acid LAV, as in Example 4(ii)and adding oxalic acid, the temperature range for high sound deadeningefficiency, has been shifted further downward to the temperature range10° to 30° C. This formulation is thus well suited to auto applicationsthat range from cold to temperate climates. A similar downward shift ofthe temperature region of highest sound deadening efficiency has beenachieved with other additives such as stearic acid, calcium stearate andlubricants including waxes.

EXAMPLE 4 (iv)

    ______________________________________                                        Weight Percentage                                                             Ingredient        Preferred                                                   ______________________________________                                        Calcium carbonate 80.1                                                        Riconoleic acid LAV                                                                             1.2                                                         PVC copolymer     5.3                                                         PVC heat stabiliser                                                                             1.1                                                         Nitrile rubber    5.3                                                         Oxalic Acid       0.0                                                         Pine rosin        6.9                                                         Irganox 565        0.03                                                       ______________________________________                                    

By decreasing the percentage of Riconoleic acid, changing the quantityof calcium carbonate and the ratio of PVC to NBR the temperature rangefor high sound deadening efficiency has been shifted upwards to between30° and 50° C. This formulation is thus well suited to dishwashingmachine application.

EXAMPLE 5

    ______________________________________                                        Weight Percentage                                                             Ingredient        Range   Preferred                                           ______________________________________                                        Calcium carbonate 40-90   79.3                                                Riconoleic acid LAV                                                                             0.1-5   1.6                                                 PVC copolymer      0-15   6.4                                                 PVC heat stabiliser                                                                             0.3-1.5 1.1                                                 Neoprene rubber    0-15   4.8                                                 Kolon 90           4-10   6.9                                                 Irganox 565       0-1      0.03                                               ______________________________________                                    

This preferred formulation has reduced slump and was found to exhibitgood sound deadening efficiency at around 21° C. but is more expensivethan previous formulations for little apparent advantage.

EXAMPLE 6 (i)

    ______________________________________                                        Weight Percentage                                                             Ingredient     Range      Preferred                                           ______________________________________                                        Filler         40-93      89.0   (calcium                                                                      carbonate)                                   Riconoleic acid LAV                                                                          0.1-5      1.3                                                 Nitrile rubber  0-15      4.2                                                 Atactic polypropylene                                                                        0-5        1.2                                                 Polar additive   0-0.5    0.0                                                 Pine rosin      3-10      4.3                                                 Irganox 565    0-1         0.03                                               ______________________________________                                    

The above preferred formulation contains no PVC, is low in cost anddisplayed excellent toughness but poor hot slump. This formulation showsvery good sound deadening efficiency in the region of 25° C. Such aformulation is interesting for roof decking.

EXAMPLE 6 (ii)

    ______________________________________                                        Weight Percentage                                                             Ingredient        Preferred                                                   ______________________________________                                        Calcium carbonate 88.9                                                        Riconoleic acid LAV                                                                             1.2                                                         Nitrile rubber    5.3                                                         Atactic polypropylene                                                                           0.0                                                         Oxalic acid       0.3                                                         Pine rosin        4.3                                                         Irganox 565        0.03                                                       ______________________________________                                    

The preferred formulation contains no PVC, is low in cost and displaysexcellent toughness but poor hot slump. This formulation shows very goodlower temperature sound deadening efficiency down to 15° C. Such aformulation is interesting where PVC is not desirable or where lowtemperature sound deadening performance is required.

EXAMPLE 6 (iii)

    ______________________________________                                        Weight Percentage                                                             Ingredient        Preferred                                                   ______________________________________                                        Calcium carbonate 88.7                                                        Riconoleic acid LAV                                                                             1.2                                                         Nitrile rubber    5.3                                                         Atactic polypropylene                                                                           0.0                                                         Phthalic anhydride                                                                              0.6                                                         Pine rosin        4.3                                                         Irganox 565        0.03                                                       ______________________________________                                    

This preferred formulation employs phthalic anhydride in a non PVCcontaining sound deadening material. It is also low in cost, anddisplayed good toughness but poor hot slump. This formulation shows goodsound deadening efficiency at lower temperatures.

EXAMPLE 6 (iv)

    ______________________________________                                        Weight Percentage                                                             Ingredient        Preferred                                                   ______________________________________                                        Calcium carbonate 69.7                                                        Alumina tri-hydrate                                                                             19.0                                                        Riconoleic acid LAV                                                                             1.2                                                         Nitrile rubber    5.3                                                         Atactic polypropylene                                                                           0.0                                                         Oxalic acid       0.6                                                         Pine rosin        4.1                                                         Irganox 565        0.03                                                       ______________________________________                                    

This preferred formulation is a flame retardant variation of Example 6(ii) and displayed similar properties.

EXAMPLE 7

    ______________________________________                                        Weight Percentage                                                             Ingredient        Range   Preferred                                           ______________________________________                                        Calcium carbonate 40-90   81.2                                                Riconoleic acid LAV                                                                             0.1-5   1.2                                                 Chlorin.polyethylene                                                                             2-15   3.7                                                 Nitrile rubber     0-15   7.5                                                 Oxalic acid         0-0.5 0.2                                                 Pine rosin         4-10   5.4                                                 Basic lead sulphate                                                                             0.3-1.5 0.8                                                 ______________________________________                                    

The preferred formulation contains chlorinated polyethylene anddisplayed good sound deadening efficiency in the region of 30° C.However is more expensive than some other formulations of similar sounddeadening efficiency.

While it has been convenient to describe the invention herein inrelation to particularly preferred embodiments and examples, it is to beappreciated that various modifications, alterations and/or additions tothe embodiments and examples described herein may be made within thescope and ambit of the present invention, as defined by the claims.

I claim:
 1. A sheet or pad of heat fusible thermoplastic sound deadeningmaterial which contains no bitumen and no asphalt, said sheet or padcomprising:(a) a polymeric component; (b) a filler pre-treated with acompatibilising agent, wherein said compatibilising agent is ricinoleicacid; and (c) a tackifier.
 2. A sheet or pad according to claim 1,wherein said compatibilising agent is ricinoleic acid LAV.
 3. A sheet orpad according to claim 2, wherein said polymeric component comprises anelastomer comprising a natural or synthetic rubber.
 4. A sheet or padaccording to claim 3, wherein said elastomer comprises nitrile rubber,butyl rubber, ethylene propylene rubber, polychloroprene, polysulphiderubber or styrene butadiene rubber.
 5. A sheet or pad according to claim2, wherein said polymeric component comprises polyvinyl chloride,chlorinated polyethylene or ethylene vinyl acetate copolymer.
 6. A sheetor pad according to claim 2, wherein said polymeric component is presentin an amount not greater than about 18% by weight of the total weight ofthe material.
 7. A sheet or pad according to claim 6, wherein saidpolymeric component is present in an amount in the range of from 3 to12% by weight of the total weight of the material.
 8. A sheet or padaccording to claim 2, wherein said compatibilising agent is present inan amount in the range of from 0.1 to 5% by weight of the total weightof the material.
 9. A sheet or pad according to claim 2, wherein saidtackifier is present in an amount in the range of from 2 to 9% by weightof the total weight of the material.
 10. A sheet or pad according toclaim 1, wherein said filler is selected from the group consisting ofcalcium carbonate, barytes, talc, mica, magnesium carbonate, silica andmixtures thereof.
 11. A sheet or pad according to claim 10, wherein saidfiller comprises calcium carbonate.
 12. A sheet or pad according toclaim 10, wherein said filler is present in an amount in the range offrom 60 to 90% by weight of the total weight of the material.
 13. Amethod for forming a heat fusible thermoplastic sound deadening materialaccording to claim 1 comprising the steps of:compatibilising a filler bytreatment with ricinoleic acid to form a pre-blend; mixing the pre-blendwith other ingredients including a polymeric component and a tackifierto form a mix; and forming a sheet or pad from said mix.
 14. A methodaccording to claim 13, wherein said filler comprises calcium carbonate.15. A method according to claim 13, wherein said polymeric componentcomprises an elastomer.
 16. A method according to claim 13, wherein saidpolymeric component comprises polyvinyl chloride, chlorinatedpolyethylene or ethylene vinyl acetate copolymer.
 17. A method forapplying a heat fusible thermoplastic sound deadening material accordingto claim 1 to a metal panel comprising the steps of:forming a sheet orpad of sound deadening material by compatibilising a filler by treatmentwith ricinoleic acid to form a pre-blend, mixing the pre-blend withother ingredients including a polymeric component and a tackifier toform a mix, and forming said sheet or pad from said mix; laying saidsheet or pad on a metal panel; and heating said metal panel and saidsheet or pad whereby to bond said sheet or pad to said metal panel. 18.A method according to claim 17, wherein said filler comprises calciumcarbonate.
 19. A method according to claim 17, wherein said polymericcomponent comprises an elastomer.
 20. A method according to claim 17,wherein said polymeric component comprises polyvinyl chloride,chlorinated polyethylene or ethylene vinyl acetate copolymer.
 21. Asheet or pad of heat fusible thermoplastic sound deadening materialwhich contains no bitumen and no asphalt, said sheet or padcomprising:(a) a polymeric component selected from the group consistingof nitrile rubber, polyvinyl chloride polymers, polyvinyl chloridecopolymers and mixtures thereof; (b) a filler comprising calciumcarbonate pre-treated with a compatibilising agent, wherein saidcompatibilising agent is ricinoleic acid; and (c) a tackifier.
 22. Asheet or pad according to claim 21, wherein said compatibilising agentis ricinoleic acid LAV.
 23. A sheet or pad according to claim 22,wherein said tackifier comprises a pine rosin.
 24. A sheet or padaccording to claim 22, wherein said compatibilising agent is present inan amount of from 0.1 to 5% by weight of the total weight of thematerial.
 25. A sheet or pad according to claim 22, wherein saidpolymeric component is present in an amount not greater than about 18%by weight of the total weight of the material.
 26. A sheet or padaccording to claim 25, wherein said polymeric component is present in anamount in the range of from 3 to 12% by weight of the total weight ofthe material.
 27. A sheet or pad according to claim 22, wherein saidfiller is present in an amount in the range of from 60 to 90% by weightof the total weight of the material.
 28. A sheet or pad according toclaim 22, wherein said tackifier is present in an amount in the range offrom 2 to 9% by weight of the total weight of the material.
 29. A sheetor pad according to claim 22 which further includes a polar additivecomprising a carboxylic acid or anhydride thereof.
 30. A sheet or padaccording to claim 29, wherein said polar additive is selected from thegroup consisting of oxalic acid, phthalic acid, malonic acid andanhydrides thereof.
 31. A sheet or pad of heat fusible thermoplasticsound deadening material which contains no bitumen and no asphaltcomprising:

    ______________________________________                                                          wt. %                                                       ______________________________________                                        PVC and/or nitrile rubber                                                                         3-30                                                      Ricinoleic Acid     0.1-5                                                     Calcium Carbonate   40-90                                                     Alumina Trihydrate  0-30                                                      Pine Rosin          4-10                                                      Oxalic Acid          0-0.5                                                    Anti-oxidant        0-1                                                       Lubricant           0-4                                                       ______________________________________                                    

and wherein said calcium carbonate is pre-treated with said ricinoleicacid.
 32. A sheet or pad according to claim 31 which further includes aheat stabilizer in an amount of 0.3 to 1.5% by weight when PVC ispresent in the sheet or pad.
 33. A sheet or pad according to claim 31,wherein said ricinoleic acid comprises ricinoleic acid LAV.
 34. A sheetor pad according to claim 31, wherein said lubricant is selected fromthe group consisting of waxes, stearic acid and calcium stearate.